Si-containing thin films are used widely in the semiconductor, photovoltaic, LCD-TFT, flat panel-type device, refractory material, or aeronautic industries. Si-containing thin films may be used, for example, as dielectric materials having electrical properties which may be insulating (SiO2, SiN, SiCN, SiCOH, MSiOx, wherein M is Hf, Zr, Ti, Nb, Ta, or Ge and x is greater than zero), Si-containing thin films may be used as conducting films, such as metal silicides or metal silicon nitrides. Due to the strict requirements imposed by downscaling of electrical device architectures towards the nanoscale (especially below 28 nm node), increasingly fine-tuned molecular precursors are required which meet the requirements of volatility (for ALD process), lower process temperatures, reactivity with various oxidants and low film contamination, in addition to high deposition rates, conformality and consistency of films produced.
It is well known that silane (SiH4) can be used for thermal CVD. However this molecule is pyrophoric which makes this room temperature gas a challenge to handle safely. CVD methods employing halosilanes (such as dichlorosilane SiH2Cl2) have been used. However, these may require long purge times, cause halogen contamination of the films and particle formation (from ammonium chloride salts), and even damage certain substrates resulting in undesirable interfacial layer formation. Partially replacing halogen with alkyl groups may yield some improvement, but at a cost of detrimental carbon contamination within the film.
Organoaminosilanes have been used as precursors for CVD of Si-containing films. U.S. Pat. No. 7,192,626 to Dussarrat et al. reports the use of trisilylamine N(SiH3)3 for deposition of SiN films. Other reported precursors include diisopropylaminosilane class of Si precursors for CVD of Si-containing films is given by the general formula (R1R2N)xSiH4−x wherein x is between 1 and 4 and the R substituents are independently H, C1-06 linear, branched, or cyclic carbon chains (see, e.g., WO2006/097525 to Dussarrat et al.).
Hunks et al. disclose a wide range of Si-containing precursors in US2010/0164057, including silicon compounds having the formula R4−xSiLx, wherein x is an integer having a value from 1 to 3R may be selected from H, branched and unbranched C1-C6 alkyl, C3-C8 cycloalkyl, and C6-C13 aryl groups; and L may be selected from isocyanato, methylethylketoxime, trifluoroacetate, triflate, acyloxy, β-diketiminate, β-di-iminate, amidinate, guanidinate, alkylamino, hydride, alkoxide, or formate ligands. Pinnavaia et al. claim a method for the preparation of a porous synthetic, semi-crystalline hybrid organic-inorganic silicon oxide composition from silicon acetylacetonate and silicon 1,3-diketonate precursors (U.S. Pat. No. 6,465,387).
Silyl esters have been reported as early as 1967 (see, e.g, E.A.V. Ebsworth et al., J. Chem. Soc. A., 1967, 69-72), but do not appear to have been used in vapor deposition methods.
Despite the wide range of choices available for the deposition of Si containing films, additional precursors are continuously sought to provide device engineers the ability to tune manufacturing process requirements and achieve films with desirable electrical and physical properties.